Selenium is one of the essential trace elements for human and animals, which is fundamental to health. Selenium-deficiency in human affects nervous system, reproductive system, immune system and cardiovascular system. Selenium-deficiency in animals often results in dysfunction in reproductive system, decrease of reproductive performance, growth inhibition, and muscle lesions (such as white muscle disease, cardiomyopathy and skeletal muscle myopathy), etc. Human and animals maintain selenium requirements by obtaining selenium from soil through food chain. People with selenium intake deficiency are facing health risks. Currently recognized as the safest and most efficient selenium supplement form is Selenomethionine (SeMet). Comparing with SeMet, elemental selenium is regarded as biological inert with neither activity nor toxicity. However, recent years, research has indicated that comparing with SeMet, nano-sized elemental selenium particles possess similar biological activity and even lower toxicity.
Selenium nanoparticle biogenesis mostly uses ascorbic acid, sodium thiosulfate, sodium sulphite or hydrazine to reduce selenium dioxide, selenite or selenate to synthesize selenium nanostructure. Chemically synthesized selenium nanostructures require surfactant or stabilizer (proteins or polysaccharides, etc.) to maintain stability, otherwise, they transform easily into black, toxic elemental selenium. In addition, the process of selenium nanostructure synthesis introduces toxic materials, which pollutes the environment. It has been proven that some bacteria could reduce selenium oxyanions to zero-valence selenium and form nanostructure particles, which are sphere shaped, uniform sized, and more stable, comparing with chemically synthesized selenium nanostructures. Moreover, bacterial fermentation isn't usually influenced by temperature and season. Bacterial fermentation for biogenic selenium nanostructure synthesis is also characterized by strong production capacity and short production cycle. Therefore, using bacteria to synthesize biogenic elemental selenium nanostructure may be a safe and efficient way for the future.
The present invention relates to a method of using E. cloacae to synthesize biogenic elemental selenium nanostructures.